Prostaglandins have been used successfully in the induction of abortion and in the treatment of pyometra, most often in combination with dopamine agonists or progesterone antagonists. They cause luteolysis followed by a decline in progesterone levels, ana have a stimulatory effect on myometrial contractions. Prostaglandin use has been associated with side effects that can be avoided or reduced using synthetic PGF2α analogues. Dopamine agonists have contributed to the effective treatment of pseudopregnancy. Dopamine agonists inhibit prolactin secretion which is necessary for the maintenance of corpus luteum in the second half of luteal phase. They are effective in inducing abortion in combination with prostaglandins, but also on their own if used after the 40th day of pregnancy. Dopamine agonists lead to shortening of the interestrus interval and induction of estrus. The mechanism by which estrus induction is achieved is not fully understood but is thought to stimulate gonadotropin secretion. The use of lactogenic drugs and their effect has not been widely studied in bitches. Aglepristone is a competitive progesterone antagonist registered for induction of abortion up to 45 days after mating. Aglepristone is effective in the treatment of closed and open pyometra and in the treatment of other progesterone-dependent physiological or pathologic conditions. Progestins, androgens and GnRH agonist are used for prevention of estrus cycle in the bitch. Deslorelin implant as GnRH agonist is registered for the induction of temporary infertility in healthy, intact, sexually mature male dogs. Primary effect of deslorelin implant in bitches is estrus induction followed by inhibitory effect on estrous cycle. The use of deslorelin is related to higher rate of anovulatory cycles and reduced pregnancy rates after estrus induction.